1. Field of the Invention
The present invention generally relates to computer-aided detection (CAD) of abnormal regions in medical imagery and, in particular, relates to providing information regarding why a particular region of the imagery was or was not displayed with a corresponding CAD system detection.
2. Discussion of Background
CAD systems are becoming widely used to assist readers of medical imagery. Such systems are commercially available to assist radiologists in the detection of signs of cancer in mammographic and chest imagery by highlighting regions of possible malignancies. In essence, the CAD systems become a second reader of the medical imagery for the radiologist.
At a fundamental level, CAD system operation may be explained as the sequence of operations, comprising, in order, detection, discrimination, and display. In detection, input imagery is analyzed to locate candidate regions with characteristics typical of malignancies. The input imagery can be from a variety of sources including digitized film and systems which directly create digital images. In mammography, separate processing paths are typically provided to individually detect common types of cancer: a mass detector and a clustered microcalcification detector. A set of measurements or features is computed from the candidate regions. The set of features is input to a discrimination process which determines whether to accept or to dismiss each candidate region. In the display step, the collection of candidate regions accepted by the discrimination step is shown to a user, typically a radiologist.
In practice, many users become accustomed to the operation of the CAD system. Most CAD system outputs are readily interpreted by users. That is, a displayed detection is either accepted as malignant or is easily dismissed as a false positive mark due to some observable artifact in the image. However, users may occasionally desire more information about the reasons a region was marked. Additionally, in some cases, it is foreseeable that users may desire more information about regions in an image that are not marked by the CAD system. Since CAD systems typically base display decisions on computed numerical scores from a plurality of measurements, there is no current method for providing feedback to a radiologist regarding why a particular image region was marked or not.
Therefore, there is a need for providing information to users regarding the factors influencing a CAD system's determination about whether or not to mark a particular region as a detection.